diff mbox series

[net] af_key: relax availability checks for skb size calculation

Message ID 20201227005021.907852-1-xiyou.wangcong@gmail.com
State New
Headers show
Series [net] af_key: relax availability checks for skb size calculation | expand

Commit Message

Cong Wang Dec. 27, 2020, 12:50 a.m. UTC 
From: Cong Wang <cong.wang@bytedance.com>

xfrm_probe_algs() probes kernel crypto modules and changes the
availability of struct xfrm_algo_desc. But there is a small window
where ealg->available and aalg->available get changed between
count_ah_combs()/count_esp_combs() and dump_ah_combs()/dump_esp_combs(),
in this case we may allocate a smaller skb but later put a larger
amount of data and trigger the panic in skb_put().

Fix this by relaxing the checks when counting the size, that is,
skipping the test of ->available. We may waste some memory for a few
of sizeof(struct sadb_comb), but it is still much better than a panic.

Reported-by: syzbot+b2bf2652983d23734c5c@syzkaller.appspotmail.com
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
 net/key/af_key.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Steffen Klassert Jan. 5, 2021, 8:09 a.m. UTC | #1 
On Sat, Dec 26, 2020 at 04:50:20PM -0800, Cong Wang wrote:
> From: Cong Wang <cong.wang@bytedance.com>

> 

> xfrm_probe_algs() probes kernel crypto modules and changes the

> availability of struct xfrm_algo_desc. But there is a small window

> where ealg->available and aalg->available get changed between

> count_ah_combs()/count_esp_combs() and dump_ah_combs()/dump_esp_combs(),

> in this case we may allocate a smaller skb but later put a larger

> amount of data and trigger the panic in skb_put().

> 

> Fix this by relaxing the checks when counting the size, that is,

> skipping the test of ->available. We may waste some memory for a few

> of sizeof(struct sadb_comb), but it is still much better than a panic.

> 

> Reported-by: syzbot+b2bf2652983d23734c5c@syzkaller.appspotmail.com

> Cc: Steffen Klassert <steffen.klassert@secunet.com>

> Cc: Herbert Xu <herbert@gondor.apana.org.au>

> Signed-off-by: Cong Wang <cong.wang@bytedance.com>


Patch applied, thanks!
diff mbox series

Patch

diff --git a/net/key/af_key.c b/net/key/af_key.c
index c12dbc51ef5f..ef9b4ac03e7b 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -2902,7 +2902,7 @@  static int count_ah_combs(const struct xfrm_tmpl *t)
 			break;
 		if (!aalg->pfkey_supported)
 			continue;
-		if (aalg_tmpl_set(t, aalg) && aalg->available)
+		if (aalg_tmpl_set(t, aalg))
 			sz += sizeof(struct sadb_comb);
 	}
 	return sz + sizeof(struct sadb_prop);
@@ -2920,7 +2920,7 @@  static int count_esp_combs(const struct xfrm_tmpl *t)
 		if (!ealg->pfkey_supported)
 			continue;
 
-		if (!(ealg_tmpl_set(t, ealg) && ealg->available))
+		if (!(ealg_tmpl_set(t, ealg)))
 			continue;
 
 		for (k = 1; ; k++) {
@@ -2931,7 +2931,7 @@  static int count_esp_combs(const struct xfrm_tmpl *t)
 			if (!aalg->pfkey_supported)
 				continue;
 
-			if (aalg_tmpl_set(t, aalg) && aalg->available)
+			if (aalg_tmpl_set(t, aalg))
 				sz += sizeof(struct sadb_comb);
 		}
 	}